Re: loaded tires and air pressure

In most cases, manufacturers recomendations are based on weight capacity as much as anything. The pressures they'll recommend aren't really "workable" numbers for many applications. That said, "too soft" is too soft. There's a practical limit for minimum AND maximum.

I've always ran between 6 and 12 psi in rears on all my tractors. Now....That's with bame brand, well made, 6 to 8 ply tires. I'd think a 4 ply "cheap-o" tire would need more psi to remain stable under a load.

All my tractors have fluid filled rears. I adjust air pressures so that I get a decent ride, the tire isn't mis-shapen under a load, and traction is close to it's maximum. There's always a "middle ground" where you can acheive the best balance of all these factors.

On my Deere 2440, I have GoodYear DynaTorque II bias ply, 16.9X30's, 6 ply. They're over 15 years old, used quite a bit, and have always been kept at/near 9psi. No sidewall failure, no abnormal wear, excellent traction (out of a tire not known for it's traction) and no issues to report.

On my Massey Ferguson 150, I've recently replaced the rear tires. The OLD set was Armstrong 14.9 x 28's, 8 ply. I ran them @ 6psi. (Heavy tire on a relatively light tractor) They lasted a little over 20 years with no abnormal wear. Now I have 13.6 x 28 Titan 6 ply "long bar/short bar". They need 8 to 9 psi to hold their shape under a load. Traction is good at that level. They're showing no wear in a year and a half of use.

You can live and die by "the book", or, you can figure out "what works". Manufacturers recomendations and owners manuals are a good starting point, but after many years and lots of hours of actual use, I've found those "rules" to be flawed for certain applications.

There are three kinds of men;
1.) The ones that learn by reading
2.) The few who learn by observation
3.) The rest of them have to pee on the electric fence for themselves.

Re: loaded tires and air pressure

My JD 3320 has 43x16.00-20 R4s on the rear. The book says 12-20psi. When I took delivery of the tractor you could slide your fingers under the edge of the tread and it rode like a rock on the road. I let them down to 15 and it was a little better. After I filled my tires with Rim Guard I inflated to 15 psi and the tire would not sit flat on the floor. You could slide a piec of paper about 3" under the edge of the tires so I was only getting about 3/4 of the tread touching the ground. I lowered the pressure to 10 and have what I feel is good tire to ground contact for the current weight on the tractor. Pressure may need to be adjusted if a heavy load is put on the 3 point.

I also loaded the front tires and put them up to full pressure for loader work.

The tires on the tractor below have 7 psi and look flat but that is what the manufacture calls for. They are around 36" wide.

Re: loaded tires and air pressure

I only check the rear tire pressure with a gauge if a customer requests it. With the heaviest mounted attachment connected and carried by the tractor, there should be one or two bars (R-1 or R-4 tread) in full contact with the ground. Bias tires should have a slight bulge at the contact point, radials a little more. The pressure to achieve these conditions will vary due to tire size and ply rating and tractor/implement weight. Whether a tire contains liquid ballast has no bearing on the proper inflartion pressure.

A properly inflated rear will have between about 8 and 20 PSI. A small compact with fat R-4's will be at the low end. An older row crop farm tractor with narrow R-1's will be at the upper end. Properly inflated or slightly underinflated rears provide a better ride and better traction than overinflated rears.

Re: loaded tires and air pressure

There is no right answer.
You want soft, and More traction use less, you want firm, and Road speed use more.
Farmer's don't need no stinking manual.
I'll bet my tires are 30 plus years old, showing age, and the same deal with them depending on load and what I'm doing.

Re: loaded tires and air pressure

Im pretty much with Philscbx...

There are a few things to consider.
1] The compression ratio inside a filled tire is much greater and so the pressure will rise quickly as the tire deflects as it begins to bear more weight.
2] How varied are the weights of the implements used.
3] How varied are the amounts of tractive force that are required to pull the load?

Due these and other incidentals I run a range of pressures decided by how the tractor looks when configured for the job at hand. I want to see 2 bars touching to the edge on each side of the tire. This gives a little bulge that I consider no problem. What I dont want is to see is much sidewall crinkle next to the tread bars under consistent pull load conditions. Any significant crinkle beyond momentary is cause for more inflation pressure. Due to the higher compressional stiffness, and the fact that the fluid filled tire has 1 to 2 psi greater internal pressure at the bottom, I find that pressures can be run 2 or 3 psi lower. Depending on the job and tractor weight I will run anywhere from 5psi up. Fronts are usually near their peak rated pressures. Rears almost never.
larry